Our long term goal is to understand the molecular mechanisms of regulation of eukaryotic mRNA gene transcription by RNA Polymerase II (Pol II). A comprehensive knowledge of transcriptional regulatory mechanisms is absolutely essential if we are to understand both normal and pathological processes and conditions, both of which are products of gene transcription events. Our studies utilize the genetically tractable Baker's Yeast, Saccharomyces cerevisiae, as a model system for elucidating the detailed role that factor TFIID plays in the complicated process of mRNA gene transcription by Pol II. These studies are an outgrowth of our ongoing analyses of TBP, the TATA-box Binding Protein which binds to the promoter of most mRNA encoding genes in order to set into motion the chain of events leading to transcription and thus gene expression. TBP appears not to exist as a free protein inside the cell, but is only functional when associated with RNA Polymerase-specific collections of additional TBP binding proteins known as TBP Associated Factors (TAFs). In yeast cells there are at least eleven TAFs which associate with TBP to form TFIID. Work from a large number of different investigators has demonstrated that the multisubunit TFIID complex is intimately involved in the regulatory events which control mRNA gene transcription. Hence, understanding the composition and function of the TFIID TBP-TAF complex, as well as other distinct TBP-TAF complexes, will be key to figuring out how gene transcription is controlled. The approach which we will use in our experiments will be multi-faceted combining biochemical and genetic analyses which focus upon yeast TBP and the genes encoding the multiple yeast TAFs which we have in cloned form. We will examine the interplay of these factors with TBP, each other, promoter DNA, and RNA polymerase II. Successful completion of these experiments will greatly increase our understanding of the all important process of mRNA gene transcription mediated by pol II.